System and method for determining a wheel-rail adhesion value for a railway vehicle

Abstract

A system for determining a wheel-rail adhesion value for a railway vehicle including at least one axle to which two wheels having a radius are coupled is provided. The system includes a deformation detection circuit coupled to an axle arranged to detect a torsional deformation of the axle due to a longitudinal adhesion force transferred from the axle to the rail, and a controller arranged to estimate a torque value as a function of the torsional deformation detected to convert the estimated torque value into the longitudinal adhesion force value as a function of the radius of the wheels, and to calculate the wheel-rail adhesion value through the ratio between the longitudinal adhesion force value and a normal load value that the axle exerts on the rail. A method for determining a wheel-rail adhesion value for a railway vehicle is also provided.

Claims

1. A system for determining a wheel-rail adhesion value for a railway vehicle, the system comprising: a deformation detection circuit coupled to an axle of the railway vehicle, the axle coupled to at least two wheels, the deformation detection circuit configured to detect a torsional deformation of the axle due to a longitudinal adhesion force transferred from the axle to a rail via the at least two wheels; and a controller configured to estimate a torque value as a function of the torsional deformation detected by the deformation detection circuit, the controller being further configured to convert the torque value into a longitudinal adhesion force value as a function of a radius of the at least two wheels coupled to the axle, and to calculate a wheel-rail adhesion value through a ratio between the longitudinal adhesion force value and a normal load value that the axle exerts on the rail via the at least two wheels, the controller configured to control application of at least one of a braking force or a tractive force to the axle based on the wheel-rail adhesion value to control movement of the railway vehicle.

2. The system of claim 1, wherein the controller is configured to convert the torque value into the longitudinal adhesion force value through a ratio between the torque value and the radius of the at least two wheels.

3. The system of claim 1, wherein the deformation detection circuit comprises at least one strain-gauge sensor.

4. The system of claim 1, wherein the deformation detection circuit comprises a bridge of multiple strain-gauge sensors.

5. The system of claim 1, wherein the deformation detection circuit comprises at least one piezoelectric sensor.

6. The system of claim 1, wherein the controller is configured to convert the torque value into the longitudinal adhesion force value by dividing the torque value by the radius of the at least two wheels.

7. The system of claim 1, wherein the controller is configured to calculate the wheel-rail adhesion value by dividing the longitudinal adhesion force value by the normal load value.

8. The system of claim 1, wherein the controller is disposed in the deformation detection circuit that is coupled to the axle.

9. The system of claim 1, wherein the controller is configured to determine the normal load value that the axle exerts on the rail via the wheels via a dynamic load measurement system.

10. The system of claim 1, wherein the controller is configured to determine the normal load value that the axle exerts on the rail via the wheels via load cells.

11. A method for determining a wheel-rail adhesion value for a railway vehicle, the method comprising: detecting a torsional deformation of an axle of the railway vehicle due to a longitudinal adhesion force transferred from the axle to a rail via at least two wheels coupled to the axle; estimating a torque value as a function of the torsional deformation that is detected; converting the torque value into a longitudinal adhesion force value as a function of a radius of the at least two wheels coupled to the axle; calculating a wheel-rail adhesion value through a ratio between the longitudinal adhesion force value and a normal load value exerted by the axle on the rail via the at least two wheels; and applying at least one of a braking force or a tractive force to the axle based on the wheel-rail adhesion value to control movement of the railway vehicle.

12. The method of claim 11, wherein the torque value is converted into the longitudinal adhesion force value through a ratio between the torque value and the radius of the at least two wheels.

13. The method of claim 11, wherein the torsional deformation of the axle is detected using at least one strain-gauge sensor.

14. The method of claim 11, wherein the torsional deformation of the axle is detected using at least one piezoelectric sensor.

15. The method of claim 11, wherein the torque value is converted into the longitudinal adhesion force value by dividing the torque value by the radius of the at least two wheels.

16. The method of claim 11, wherein the wheel-rail adhesion value is calculated by dividing the longitudinal adhesion force value by the normal load value.

17. The method of claim 11, further comprising determining the normal load value that the axle exerts on the rail via the wheels via a dynamic load measurement system.

18. The method of claim 11, further comprising determining the normal load value that the axle exerts on the rail via the wheels via load cells.

19. The method of claim 11, further comprising coupling a deformation detection circuit to the axle, the deformation detection circuit configured to detect the torsional deformation of the axle.

20. The method of claim 19, wherein at least the estimating, converting, and calculating steps of the method are performed by a controller that is disposed in the deformation detection circuit coupled to the axle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an axle of a railway vehicle resting on a rail, and the contact forces, broken down into three spatial directions, which identify the vertical forces, lateral forces and longitudinal forces;

(2) FIG. 2 shows a block diagram illustrating the steps usually taken by systems built according to the prior art;

(3) FIG. 3 illustrates an axle of a railway vehicle to which a deformation detection circuit is coupled; and

(4) FIG. 4 illustrates, by way of example, the signal generated by the deformation detection circuit subjected to a torsional deformation during the movement of a train.

DETAILED DESCRIPTION

(5) Before describing in detail a plurality of embodiments of the present invention, it should be clarified that the invention is not limited in its application to the details of construction and to the configuration of the components presented in the following description or illustrated in the drawings. The invention may assume other embodiments and may be implemented or achieved in different ways. It should also be understood that the phraseology and terminology have descriptive purposes and should not be construed as limiting. The use of “include” and “comprise” and the variations thereof are to be understood as encompassing the elements stated hereinafter and the equivalents thereof, as well as additional elements and the equivalents thereof.

(6) Moreover, throughout the present description and in the claims, terms and expressions indicating positions and orientations, such as “longitudinal”, “transverse”, “vertical” or “horizontal”, refer to the direction of travel of the train.

(7) FIG. 3 illustrates, by way of example, an axle 1 of a railway vehicle to which is coupled a deformation detection circuit 10 belonging to the system for determining a wheel-rail adhesion value according to the present invention.

(8) In one embodiment of the invention, the system for determining a wheel-rail adhesion value for a railway vehicle that includes at least one axle 1 with two wheels having a radius R coupled thereto, comprises a deformation detection circuit 10 coupled to an axle 1 of the railway vehicle.

(9) The deformation detection circuit is provided to detect a torsional deformation of the axle due to a longitudinal adhesion force F.sub.long (along the direction of travel of the train) transferred by the axle to the rail.

(10) The system for determining a wheel-rail adhesion value further comprises a controller provided to estimate a torque value as a function of the torsional deformation detected by the deformation detection circuit.

(11) The controller is further provided to convert the estimated torque value into a longitudinal adhesion force value F.sub.long as a function of the radius R of the wheels, and to calculate a wheel-rail adhesion value through the ratio between said longitudinal adhesion force value F.sub.long and a normal load value that the axle exerts on the rail.

(12) The normal load value may be determined by the static mass acting on the axle or by known dynamic load measurement systems (e.g. load cells, suspension pressure, etc.).

(13) The conversion of the estimated torque value into a longitudinal adhesion force value F.sub.long may be done, for example, by means of a ratio between the estimated torque value and the value of the radius R of the wheels by said controller. The formula used for the conversion may be, for example, the following:
Adhesion force[N]=Torque [Nm]/R [m];

(14) The controller may be arranged locally close to, or directly in, the deformation detection circuit 10. Alternatively, the controller may be arranged remotely relative to the deformation detection circuit 10 in other vehicle on-board control units or in remote control stations relative to the railway vehicle. Therefore, the controller may receive data from the deformation detection circuit either via special wiring or via a wireless connection (telemetry).

(15) The controller may be a control unit, a processor or a microcontroller.

(16) In other words, referring to the evaluation of torsional deformation of FIG. 4, the mean value of the torsional stress to which the axle is subjected is correlated to the longitudinal forces exchanged between the wheels of the axle and the rail.

(17) If the vehicle is stationary and no external torques are applied to the axle (e.g. traction or braking torques), the torsional component obtained from the strain gauge measurements is zero.

(18) If the vehicle is moving and the axle is not subjected to either a traction force or a braking force (coasting state), the mean value of the torsional component is zero, even though it has a periodic oscillation linked to the rotational frequency and the natural frequency of the axle (typically on the order of 70 Hz).

(19) If, on the other hand, external torques are applied to the axle, such as a braking torque or a traction torque, the axle is subjected to torsional stress.

(20) The output signal from the deformation detection circuit 10 has an average value proportional to the longitudinal adhesion force F.sub.long transferred from the axle to the rail, with the opposite sign depending on whether it is a traction action or a braking action.

(21) The deformation detection circuit 10 may comprise at least one strain gauge sensor and/or at least one piezoelectric sensor.

(22) For example, in the above-described case, the deformation detection circuit may be made using a known Wheatstone bridge configuration. In other words, the deformation detection circuit 10 comprises a strain gauge sensor bridge, configurable with the known “quarter bridge”, “half bridge” or “full bridge” variants.

(23) To improve measurement accuracy, there may be more than one strain gauge sensors and/or piezoelectric sensors.

(24) The longitudinal force F.sub.long transferred from the axle to the rail is the adhesion force.

(25) The adhesion coefficient μ is by definition the ratio of the longitudinal adhesion force F.sub.long and the normal load force F.sub.vert. That is to say:
μ=Adhesion force/Normal load force.

(26) The present invention further provides a method for determining a wheel-rail adhesion value for a railway vehicle including at least one axle to which two wheels having a radius R are coupled, the method comprising the steps of: detecting a torsional deformation of the axle due to a longitudinal adhesion force F.sub.long transferred from the axle to the rail; estimating a torque value as a function of the detected torsional deformation; converting the estimated torque value into a longitudinal adhesion force value F.sub.long according to the radius R of the wheels; and calculating a wheel-rail adhesion value through the ratio between said longitudinal adhesion force value F.sub.long and a normal load value exerted by the axle on the rail.

(27) The conversion of the estimated torque value into a longitudinal adhesion force value F.sub.long may be done, for example, by means of a ratio between the estimated torque value and the value of the radius R of the wheels.

(28) The advantage provided by the present invention is that it allows an estimation of the longitudinal forces starting from the torsional deformations of the axle.

(29) A further advantage consists in allowing a measurement of a direct wheel-rail adhesion value to be obtained as a function of the longitudinal force transferred to the rail, i.e., by estimating an effective force for braking or traction of the axle, without the need to estimate the braking or traction forces applied.

(30) Different aspects and embodiments of a system and a method for determining a wheel-rail adhesion value according to the invention have been described. It is to be understood that each embodiment may be combined with any other embodiment. The invention, moreover, is not limited to the described embodiments, but may vary within the scope of protection as described and claimed herein.